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Seismo-ionospheric anomalies before M7.2 Haiti earthquake of August 14, 2021, from GPS TEC

Thomas Jewel E., Ben Ubong C., Ekanem Aniekan M., George Nyakno J., Nathaniel Ekong U.

Acta Geophysica

2022

Vol. 70, no 6

2621--2627

Satellite-based measurements of total electron content (TEC) have been employed extensively to detect seismo-ionospheric anomalies. In this research, analysis of Global Positioning System (GPS) and TEC data obtained from three stations within seismogenic zone of M7.2 Haiti earthquake (EQ) of August 14, 2021, has been considered. A statistical procedure was used on daily TEC for the detection of anomalous and differential TEC. The study showed both reduction and enhancement in diurnal TEC within the investigative period on days −14,−11,−9,−7,−6, −4, −3, −1, 2, 3, and 4. Based on results, the three stations on days −11, −9, and −6 were concurrently perturbed. The outcomes of the analysis, which were constrained by data of synchronously monitoring geomagnetic indices of Kernnifzer digit (kp), disturbance storm time (Dst), solar indices (sunspot number (SSN) and F10.7 cm), revealed 82% seismic-induced anomalies relating to the EQ. The differential TEC |∆TEC| data were mostly remarkable on −6 and −4 days to the EQ, and this called for spatial mapping of TEC indices for August 8 and 10, 2021, over the epicenter of the EQ in order to check for atypical UT hours. Unusual ionospheric clouds from 16:00 to 20:00 UT enveloped the epicenter. Thus, this study has uncovered strong seismo-ionospheric anomalies from GPS-TEC data related to M7.2 Haiti EQ of August 14, 2021. This work is promising as short-term precursor of EQ in order to alleviate loss of lives and properties associated with this particular seismic event among others.

On the signifcance of requisite criteria in detecting pre earthquake ionospheric precursors: a case study of the Tohoku earthquake of March 11, 2011

Chukwuma Victor U., Adekoya Bolarinwa J., Thomas Jewel E., Emah Joseph B., Oloruntola Racheal F.

Acta Geophysica

2021

Vol. 69, no. 4

1545--1566

In the advent of the Tohoku earthquake (Mw 9.1 occurred at 14:46 LT on March 11, 2011), the Japan Meteorological Agency issued earthquake early warning announcements to the general public; however, there were problems with the precision of the early warning systems. This early warning systems issue, and the scale of consequential loss of human, material and technological resources of the Tohoku earthquake and those of about 57 earthquakes with magnitude M ≥ 7.5 from August 2008 to August 2018 around the world compel a need for investigation for detection of some signals before the earthquake that should be examined and interpreted as a precursor by examining the changes in the ionospheric phenomena. In this light, discrimination of pre-earthquake ionospheric anomalies of seismic origin from those of other drivers is essential for understanding, justifcation and physical interpretation of the earthquake precursors phenomena. Presently using a set of criteria that adequately diferentiates pre-earthquake anomaly of seismic origin from those of other sources, this study has shown concordant results with the existing studies namely that foF2 data obtained from 8 Chinese and Japanese stations revealed signifcant enhancements 2–6 days before the Tohoku earthquake and that the anomalies extended to 2774 km from the epicentre, thereby underscoring the necessity of requisite criteria in detecting pre-earthquake ionospheric precursors. Furthermore, the study suggests that the anomalous variations observed during periods of earthquake preparation are of seismo-magnetosphere origin.